1. Field of the Invention
The present invention relates to a polishing body, polishing apparatus, polishing apparatus adjustment method and polished film thickness or polishing endpoint measurement method which are suitable for use in the polishing of semiconductor devices in a method for manufacturing semiconductor devices such as ULSI devices, etc., and to a semiconductor device manufacturing method.
2. Discussion of the Related Art
As semiconductor integrated circuits have become finer and more highly integrated, the individual processes involved in semiconductor manufacturing processes have become more numerous and complicated. However, the surfaces of semiconductor devices are not always flat. The presence of step differences on the surfaces of semiconductor devices leads to step breakage of wiring and local increases in resistance, etc., and thus causes wiring interruptions and drops in electrical capacitance. Furthermore, in insulating films such step differences also lead to a deterioration in the withstand voltage and the occurrence of leaks.
Meanwhile, as semiconductor integrated circuits have become finer and more highly integrated, the wavelengths of light sources in semiconductor exposure apparatuses used in photolithography have become shorter, and the numerical aperture or so-called NA of the projection lenses used in such semiconductor exposure apparatuses has become larger. As a result, the focal depth of the projection lenses used in such semiconductor exposure apparatuses has become substantially shallower. In order to deal with such increasing shallowness of the focal depth, there is a demand for even greater planarization of the surfaces of semiconductor devices than that achieved so far.
Specifically, planarization techniques such as that shown in FIG. 1 have become essential in semiconductor manufacturing processes. A semiconductor device 14, and inter-layer insulating film 12 comprising SiO2 and a metal film 13 comprising Al are formed on the surface of a silicon wafer 11. FIG. 1(a) shows an example of the planarization of an inter-layer insulating film 12 on the surface of the semiconductor device. FIG. 1(b) shows an example in which a so-called damascene is formed by polishing a metal film 13 on the surface of the semiconductor device.
A chemical mechanical polishing or chemical mechanical planarization (hereafter referred to as xe2x80x9cCMPxe2x80x9d) technique is widely used as a method for planarizing the surfaces of such semiconductor devices. Currently, the CMP technique is the sole method that can be used to planarize the entire surface of a silicon wafer.
CMP was developed on the basis of silicon wafer mirror surface polishing methods. FIG. 2 is a schematic structural diagram of a polishing (planarization) apparatus used in CMP. This polishing apparatus is constructed from a polishing member 15, an object of polishing holding part (hereafter referred to as a xe2x80x9cpolishing headxe2x80x9d in some instances) 16, and a polishing agent supply part 18. Furthermore, a silicon wafer 17 which is the object of polishing is attached to the polishing head 16, and the polishing agent supply part 18 supplies a polishing agent (slurry) 19. The polishing member 15 is formed by attaching a polishing body (hereafter referred to as a xe2x80x9cpolishing padxe2x80x9d in some instances) 21 to the surface of a platen 20.
The silicon wafer 17 is held by the polishing head 16, so that they are caused to oscillate while being rotated, and is pressed against the polishing body 21 of the polishing member 15 with a specified pressure. The polishing member 15 is also rotated, so that a relative motion is performed between the polishing member 15 and the silicon wafer 17. In this state, the polishing agent 19 is supplied to the surface of the polishing body 21 from the polishing agent supply part 18. The polishing agent 19 diffuses over the surface of the polishing body 21, and enters the space between the polishing body 21 and the silicon wafer 17 as the polishing member 15 and silicon wafer 17 move relative to each other, so that the polishing surface of the silicon wafer 17 is polished. Specifically, good polishing is accomplished by a synergistic effect of the mechanical polishing caused by the relative motion of the polishing member 15 and silicon wafer 17 and the chemical action of the polishing agent 19.
The relationship between the amount of polishing of a silicon wafer and the above-mentioned polishing conditions is given by an empirical formula known as the formula of Preston, which is indicated by Equation (1).
R=Kxc3x97Pxc3x97Vxe2x80x83xe2x80x83(1)
Here, R is the amount of polishing of the silicon wafer, P is the pressure per unit area with which the silicon wafer is pressed against the polishing body, V is the relative linear velocity caused by the relative motion between the polishing member and the silicon wafer, and k is a proportionality constant.
Conventionally, the endpoint of CMP polishing has been determined by time control using the formula of Preston on the basis of the polishing rate calculated by means of film thickness measurement using an ellipsometer, etc., after polishing several tens of dummy samples and performing a cleaning process. In CMP, however, variation occurs in the polishing rate because of the temperature distribution of the polishing body and local differences in the polishing agent supply conditions. Furthermore, because of variations in the surface conditions of the polishing body, the polishing rate drops with the number of wafers processed, and there are differences in the polishing rate due to individual differences between polishing bodies, etc. Accordingly, it is difficult to determine the endpoint of polishing by performing a specified amount of polishing using time control.
Furthermore, the time control method requires polishing work using as many as several tens of dummy samples in order to determine the polishing rate. Accordingly, this polishing work results in increased costs, and is therefore undesirable for stabilizing the semiconductor device manufacturing process and reducing production costs.
Accordingly, methods in which the endpoint of polishing is determined while measuring the motor torque or vibration, etc., in situ have been proposed as a substitute for endpoint determination by time control. Such methods are effective in the case of CMP wherein the material of the object of polishing varies (e.g., CMP of wiring materials or CMP in which there are stopper layers). However, in the case of silicon wafers having complicated patterns, there is little variation in the material of the object of polishing. Accordingly, there are cases in which it is difficult to ascertain the endpoint. Furthermore, in the case of CMP of inter-layer insulating films, it is necessary to control the inter-wiring capacitance. Accordingly, control of the residual film thickness is required rather than control of the polishing endpoint. It is difficult to measure the film thickness using a method in which the endpoint is ascertained by in-situ measurement of the motor torque or vibration, etc.
Recently, optical measurements, especially in-situ endpoint detection and in-situ film thickness measurement based on the measurement of spectroscopic reflections, have come to be viewed as effective means of solving the above-mentioned problems. For instance, one example of such measurement is described in U.S. Pat. No. 5,433,651. For such in-situ measurements, a common method is a method in which an opening part 22 used for measurement is formed in the platen 20 and polishing body 21 a shown in FIG. 2, and the surface of the object of polishing is observed by means of a polished-state measuring device 23 that measures the polished state via this opening part 22. Although not shown in FIG. 2, a transparent window is generally installed in the polishing body 21, etc., in order to close off the opening part. By installing such a window, it is possible to allow the measurement light from the polished-state measuring device 23 to pass through the window, while preventing the polishing agent 19 from leaking into the polished-state measuring device 23 via the opening part 22. In cases where no window is installed, the slurry, water and other components used in cleaning, etc., leak from this area. As a result, a complicated mechanism is required, so that the apparatus becomes complicated.
A so-called foam polishing pad comprising a foam polyurethane has been used in the past as the polishing body 21. However, in the case of foam polyurethane polishing pads, the polishing agent causes clogging, so that the polishing characteristics are unstable. Accordingly, in the case of foam polyurethane polishing pads, dressing of the polishing pad surface is generally performed using of a diamond grinding wheel in order to perform stable polishing. Dressing is a treatment which removes the polishing agent that has clogged the surface of the polishing pad, and which at the same time cuts away the surface of the foam polyurethane polishing pad, so that a fresh polishing pad surface is created. Recently, non-foam polishing bodies that do not require dressing have also begun to be used.
In cases where a window used for measurement is formed in the polishing pad for the purpose of performing the above-mentioned optical measurements, because the polishing body is generally not transparent, it is necessary to install a transparent material that differs from the material of the polishing body in the area where the window is formed. Since this material generally differs from the material of the polishing body in terms of mechanical properties, there is a serious danger that this material will cause differences in the polishing rate, polishing non-uniformities, and scratching. Furthermore, problems also arise from the window becoming scratched so that it becomes optically opaque when the polishing body (polishing pad) is cut away during the above-mentioned dressing. As a result, measurements become impossible.
Furthermore, since the polishing agent is discharged onto the polishing body during polishing, observation must be performed through the polishing agent as well. Since the polishing agent, which is dispersive, causes attenuation of the measurement light, the amount of polishing agent interposed in the measurement light path should be small when high-precision measurements are being performed. Specifically, if there is a step difference between the surface of the polishing body and the surface of the window on the side of the object of polishing, the polishing agent will accumulate in the opening part, thereby causing attenuation of the measurement light. Accordingly, it is better if there is no such step difference.
Furthermore, to reduce the intensity loss of the light that is used to measure the polished state, it is desirable to form an anti-reflection film on the opposite surface of the window from the side of the silicon wafer. However, in cases where an anti-reflection film is formed on a window that is manufactured from a soft material, cracks are formed in the anti-reflection film as a result of the bending of the window. Furthermore, since the glass transition temperature of the window is low, the window may expand or contract as a result of temperature changes, so that cracks are formed in the anti-reflection film. Accordingly, in cases where the window is manufactured from a soft material, formation of an anti-reflection film is difficult.
Furthermore, in cases where a soft transparent material that does not cause scratching of the silicon wafer, e.g., a polyurethane, nylon or soft acrylic resin, etc., is disposed in the opening part, the pressure that is applied to the window fluctuates when the opening part moves beneath the silicon wafer as a result of the rotation of the platen. Accordingly, the window that is installed undergoes deformation, thus causing optical distortion. As a result of this distortion, the window acts as a lens, etc., so that that detection of the polishing endpoint and measurement of the film thickness become unstable.
Furthermore, the problem of erroneous measurement arises in cases where the polished film thickness or polishing endpoint is measured without a constant thickness of the polishing agent between the window and the object of polishing.
The first aspect of the present invention is to solve the above-mentioned problems, and to provide a polishing body which is used in a polishing apparatus that is capable of measuring the polished state by means of light, namely a polishing body that does not cause instability in polishing, a polishing body which has a measurement window that does not require a complicated mechanism, a polishing body that does not suffer from problems such as scratching during dressing, etc., and a polishing body that does not cause instability in the detection of the polishing endpoint in situ, and a polishing apparatus which uses such polishing bodies.
Furthermore, the first aspect of the present invention also includes the provision of a polishing apparatus which is capable of measuring the polished state by means of light, and in which there is no scratching of the polishing body or instability in measurement, and a polishing apparatus adjustment method and polishing endpoint determination method in which there is no erroneous measurement in the measurement of the polished film thickness or polishing endpoint.
The second aspect of the present invention is to provide a semiconductor device manufacturing method in which the process is made more efficient by reducing the cost of the polishing process and detecting the polished state with good precision as a result of the use of the polishing apparatus, polishing apparatus adjustment method and polishing endpoint determination method, and which therefore makes it possible to manufacture semiconductor devices at a lower cost than conventional semiconductor device manufacturing methods.
A first embodiment of the present invention which is used in order to achieve the first aspect is a polishing body used in a polishing apparatus which is equipped with a polishing head that holds the object of polishing and a polishing body, and which polishes the object of polishing by causing relative motion between the polishing body and the object of polishing in a state in which a polishing agent is interposed between the polishing body and the object of polishing; the polishing body comprising one or more opening parts which are used to allow the passage of measurement light that optically measures the surface that is being polished on the object of polishing are formed in the polishing body, window plates that are transparent to at least the measurement light are fit into the opening parts, and the gap between the outermost surface of the polishing body (i.e., the surface that contacts the object of polishing) and the surfaces of the window plates on the side of the outermost surface in an unloaded state is adjusted so that this gap is greater than the amount of compressive deformation of the polishing body that occurs when the polishing load is applied.
In the present invention, the gap between the outermost surface of the polishing body and the surfaces of the window plates on the side of the outermost surface (hereafter referred to as the xe2x80x9cupper surfacesxe2x80x9d of the window plates in some instances) in an unloaded state is adjusted so that this gap is greater than the amount of compressive deformation of the polishing body that occurs when the polishing load is applied. Accordingly, even if the polishing body should contract as a result of compressive deformation when the polishing load is applied, the outermost surface of the polishing body will be closer to the object of polishing than the outermost surfaces of the window plates. Accordingly, even when the polishing load is applied, the window plates will not contact the object of polishing; consequently, scratching of the window plates can be prevented.
A second embodiment of the present invention which is used in order to achieve the first aspect is a polishing body used in a polishing apparatus which is equipped with a polishing head that holds the object of polishing and a polishing body, and which polishes the object of polishing by causing relative motion between the polishing body and the object of polishing in a state in which a polishing agent is interposed between the polishing body and the object of polishing; this polishing body being characterized by the fact that one or more opening parts which are used to allow the passage of measurement light that optically measures the surface that is being polished on the object of polishing are formed in the polishing body, window plates that are transparent to at least the measurement light are fit into the opening parts, and the window plates are constructed by laminating two or more plates comprising transparent materials.
In the present invention, the window plates disposed in the opening parts are formed by laminates of two or more plates comprising transparent materials. Accordingly, in one window, the compressive elastic modulus (hardness) of the surface located on the side of the object of polishing and the compressive elastic modulus (hardness) of the surface located on the opposite side from the object of polishing can be caused to differ by varying the compressive elastic modulus (hardness) of the transparent material located on the side of the object of polishing and the compressive elastic modulus (hardness) of the other transparent material(s). Accordingly, the compressive elastic modulus (hardness values) of the respective window materials can be set at ideal values, so that the compressive elastic modulus (hardness) of each window as a whole can also be set at an ideal value. Furthermore, the present invention can also be applied to the first embodiment of the invention.
A third embodiment of the present invention which is used in order to achieve the first aspect is the invention of the second embodiment, which is further characterized by the fact that the window plates each comprising two plates of transparent materials that are laminated together, and by the fact that among these plates of transparent materials, the compressive elastic modulus of the transparent material plate that is located on the side of the object of polishing is set at a smaller value than the compressive elastic modulus of the transparent material plate that is located on the opposite side from the object of polishing.
As a result, the transparent material plate located on the opposite side from the object of polishing comprising a material that has a large compressive elastic modulus (i.e., a hard material). Accordingly, deformation of the windows is eliminated, so that there is no instability in the detection of the polishing endpoint or instability in the measurement of the film thickness due to deformation of the windows.
A fourth embodiment of the present invention which is used in order to achieve the first aspect of the invention is the second and third embodiments, which is further characterized by the fact that the compressive elastic modulus e of the transparent material on the side of the object of polishing (among the transparent materials) is such that 2.9xc3x97107Paxe2x89xa6exe2x89xa61.47xc3x97109 Pa, and is more or less the same as the compressive elastic modulus of the polishing body.
As a result, since the compressive elastic modulus of the transparent material on the side of the object of polishing has more or less the same value as the compressive elastic modulus of the polishing body, scratching of the object of polishing as a result of the window material protruding from the surface of the polishing body and contacting the object of polishing when deformation of the window material is caused by the load applied during polishing is eliminated. Furthermore, non-uniform polishing is also eliminated.
A fifth embodiment of the present invention which is used in order to achieve the first aspect is a polishing body used in a polishing apparatus which is equipped with a polishing head that holds the object of polishing and a polishing body, and which polishes the object of polishing by causing relative motion between the polishing body and the object of polishing in a state in which a polishing agent is interposed between the polishing body and the object of polishing; the polishing body comprising one or more opening parts which are used to allow the passage of measurement light that optically measures the surface that is being polished on the object of polishing are formed in the polishing body, window plates that are transparent to at least the measurement light are fit into the opening parts, and the surfaces of the window plates on the side of the object of polishing are recessed with respect to the surface of the polishing body, with the amount of this recess being varied in a stepwise or continuous manner.
In such a polishing body, the amount of recess of the window plates with respect to the surface of the polishing body varies; accordingly, even if scratches are formed in the surfaces of the window plates by dressing or polishing due to deformation of the polishing body, etc., the extent of the scratches is limited to a certain area. Accordingly, in cases where such scratching occurs, in-situ measurement of the polished state can be accomplished by selecting an area that is free of scratches, and using this area to observe the polished surface of the object of polishing, so that the frequency of replacement of the polishing body or window plates can be reduced. As a result, the cost of polishing can be reduced.
Furthermore, since the polishing agent enters the areas between the portions corresponding to the surface parts of the polishing body in the opening parts and the surface parts of the window plates, so that the measurement light is absorbed by a corresponding amount, it is desirable that the amount of recess be as small as possible. However, if this amount of recess is set at a shallow value, the windows tend to be scratched for the reasons described above. The present invention solves this trade-off. Specifically, this trade-off is solved by performing in-situ measurements using opening parts in which the amount of recess is as small as possible, and using unscratched portions in areas where the amount of recess is deep in cases where the windows become scratched.
A sixth embodiment of the present invention which is used in order to solve the first aspect of the present invention is the fifth embodiment, which is further characterized by the fact that the polishing body has a plurality of the opening parts, and the amount of recess varies in a stepwise manner as a result of this amount of recess being different in each of the opening parts.
As a result, when the polished state of the object of polishing is observed by means of the device that measures the polished state, even if the windows in the opening parts in which the amount of recess is small are scratched as a result of dressing or polishing, there is no scratching of the windows in the opening parts in which the amount of recess is large. Accordingly, for the reasons described above, in-situ measurement of the polished state can be accomplished by first using opening parts in which the amount of recess is small for measurement, and then, in cases where these windows become scratched, switching the observation of the polished state of the object of polishing by means of the device that measures the polished state to windows in opening parts in which the amount of recess in the initial state is different, so that the windows are unscratched.
A seventh embodiment of the present invention which is used in order to achieve the first aspect of the present invention is the fifth embodiment, which is further characterized by the fact that the amount of recess varies in a stepwise manner as a result of this amount of recess being different in two or more portions within the same opening part.
As a result, in cases where a portion of a window plate being used for measurement (in most cases, a portion in which the amount of recess is small) becomes scratched during the observation of the polished state of the object of polishing by means of the device that measures the polished state, in-situ measurement of the polished state can be accomplished by switching the observation of the polished state of the object of polishing by means of the device that measures the polished state to a portion of the window plate in which the amount of recess in the initial state is different, so that this portion of the window plate is unscratched.
An eighth embodiment of the present invention which is used in order to achieve the first aspect of the present invention is the fifth embodiment, which is further characterized by the fact that the window plates are parallel flat-plate-form transparent plates, and the window plates are installed at an inclination with respect to the surface of the above-mentioned polishing body, so that the amount of recess varies in a continuous manner.
As a result, in cases where a portion of a window plate being used for measurement (in most cases, a portion in which the amount of recess is small) becomes scratched during the observation of the polished state of the object of polishing by means of the device that measures the polished state, in-situ measurement of the polished state can be accomplished by switching the observation of the polished state of the object of polishing by means of the device that measures the polished state to a portion of the window plate in which the amount of recess in the initial state is different, so that this portion of the window plate is unscratched.
A ninth embodiment of the present invention which is used in order to achieve the first aspect is a polishing body used in a polishing apparatus which is equipped with a polishing head that holds the object of polishing and a polishing body, and which polishes the object of polishing by causing relative motion between the polishing body and the object of polishing in a state in which a polishing agent is interposed between the polishing body and the object of polishing; the polishing body comprises one or more opening parts which are used to allow the passage of measurement light that optically measures the surface that is being polished on the object of polishing are formed in the polishing body, window plates that are transparent to at least the measurement light are fit into the opening parts, the surfaces of the window plates on the side of the object of polishing are recessed with respect to the surface of the polishing body, and the window plates are constructed from a plate material comprising a plurality of sheets of a transparent material that can be stripped away.
In the present means, in cases where the surface of a window plate that is being used for measurement becomes scratched when the polished state of the object of polishing is observed by means of the device that measures the polished state, in-situ measurement of the polished state can be accomplished by stripping away the scratched plate material, so that the underlying plate material is exposed at the surface of the window plate.
A tenth embodiment of the present invention which is used in order to achieve the first aspect of the present invention is any of the first through ninth embodiments, which is further characterized by the fact that the minimum value G of the gap between the outermost surface of the polishing body and the surfaces of the window plates on the side of the outermost surface is such that 0 xcexcm less than Gxe2x89xa6400 xcexcm.
In cases where an ordinary polishing agent is considered, if the gap G (amount of recess) between the outermost surface of the polishing body and the surfaces of the window plates on the side of the outermost surface exceeds 400 xcexcm, the measurement light is absorbed by the polishing agent that enters this gap (hole), so that it becomes difficult to measure the state of the polished surface of the object of polishing. Accordingly, it is desirable that this gap be 400 xcexcm or less in positions where the measurement light passes through. In cases where this gap (depth) differs according to location within a single opening part or between different opening parts, measurements can be performed using portions where the gap is within this range, as along as the minimum value G of the gap between the outermost surface of the polishing body and the surfaces of the window plates on the side of this outermost surface is set so that this minimum value is within the range. Furthermore, since the amount of recess is at least greater than zero, contact between the window plates and the object of polishing is eliminated.
An eleventh embodiment of the present invention which is used in order to achieve the first aspect of the present invention is any of the first through ninth embodiments, which is further characterized by the fact that the minimum value G of the gap between the outermost surface of the polishing body and the surfaces of the window plates on the side of the outermost surface is such that 10 xcexcm less than Gxe2x89xa6200 xcexcm.
As was described above, it is desirable that the minimum value G of the gap between the outermost surface of the polishing body and the surfaces of the window plates on the side of this outermost surface be 400 xcexcm or less. In the present invention, however, this gap G is limited to 200 xcexcm or less as an even more desirable range. Furthermore, this gap G is limited to 10 xcexcm or greater as a desirable range that tends to prevent the window plates from flying off of the surface of the polishing body.
A twelfth embodiment of the present invention which is used in order to solve the above mentioned problems is any of the first through ninth embodiments, which is further characterized by the fact that the gap G between the outermost surface of the polishing body and the surfaces of the window plates on the side of the outermost surface (the maximum value of G in cases where the gap G differs within a single opening part or between different opening parts) is such that 0 xcexcm less than Gxe2x89xa6(90% of the thickness of the polishing body), and the thickness t of the window plates (the minimum value of the thickness t in cases where this thickness t differs within a single opening part or between different opening parts) is such that txe2x89xa7(10% of the thickness of the polishing body).
As a result, contact between the windows and the object of polishing is eliminated, so that there is no scratching of the object of polishing or scratching of the windows. Furthermore, since the depth of the recessed parts is not too deep, the attenuation of the measurement light caused by slurry entering the recessed parts so that stable measurement becomes impossible can be prevented. Moreover, since the thickness of the windows is not too thin, deformation of the windows can be eliminated, so that there is no instability in the detection of the polishing endpoint or instability in the measurement of the film thickness due to deformation of the windows.
A thirteenth embodiment of the present invention which is used in order to solve the above-mentioned problems is any of the first through twelfth embodiments, which is further characterized by the fact that at least the surfaces of the window plates located on the side of the object of polishing are coated with a hard coating.
In spite of the fact that the gap between the outermost surface of the polishing body and the surfaces of the window plates on the side the outermost surface is set with the load during polishing being taken into account so that the window plates do not contact the wafer or the retainer ring of the polishing head, the window plates may on rare occasions make unexpected contact with the wafer or retainer ring of the polishing head due to irregular vibrations during polishing, so that scratching occurs. Accordingly, in order to prevent this, it is desirable that at least the surfaces of the window plates that are located on the wafer side be coated with a hard coating.
A fourteenth embodiment of the present invention which is used in order to achieve the first aspect of the present invention is any of the first through thirteenth, which is further characterized by the fact that the transmissivity of the window plates with respect to the measurement light is 22% or greater.
In cases where measurement of the polished state or determination of the polishing endpoint is performed in situ using measurement light, the measurement light passes through the window plate and the slurry present on the window plate, and is then reflected by the object of polishing, so that the measurement light again passes through the slurry and window plate, after which the measurement light is detected by a detector. Considering the maximum value of the light that is ordinarily absorbed by the slurry present on the window plates, if the transmissivity of the window plates alone is not 22% or greater, the amount of emitted light that does not return to the detector will be 1% or greater, so that measurement may become unstable. Accordingly, it is desirable that the transmissivity of the window plates with respect to the measurement light be set at 22% or greater.
A fifteenth embodiment of the present invention which is used in order to achieve the first aspect is a polishing body which is characterized by the fact that in a polishing body used in a polishing apparatus which is equipped with a polishing head that holds the object of polishing and a polishing body, and which polishes the object of polishing by causing relative motion between the polishing body and the object of polishing in a state in which a polishing agent is interposed between the polishing body and the object of polishing, the polishing body comprising a material that is transparent to at least the measurement light in order to allow the passage of light used for the optical measurement of the polished surface of the object of polishing.
In the present invention, the polishing body itself is constructed from a material that is transparent to the measurement light; accordingly, there is no need to form opening parts in the polishing body in order to allow the passage of this measurement light. Consequently, there is no absorption of the measurement light as a result of the polishing agent flowing into opening parts, so that measurements can be performed using a light source whose light is weaker by a corresponding amount.
A sixteenth embodiment of the present invention which is used in order to achieve the first aspect is a polishing apparatus which is characterized by the fact that in a polishing apparatus which is equipped with a polishing head that holds the object of polishing and a polishing body, and which polishes the object of polishing by causing relative motion between the polishing body and the object of polishing in a state in which a polishing agent is interposed between the polishing body and the object of polishing, the polishing body is the polishing body of any one of the first through fifteenth embodiments.
In the present invention, the polishing body of any one of the first through fifteenth embodiments is used; accordingly, the actions and effects of the respective polishing bodies can be exhibited, so that the aspect of the present invention can be achieved.
A seventeenth embodiment of the present invention which is used in order to achieve the first aspect is the polishing apparatus of the sixteenth embodiment, which is further characterized by the fact that in an apparatus having a function in which measurement light is directed onto the object of polishing from a light-projecting device via the window plates and the opening parts, this light is reflected by the object of polishing, and the returning light that again passes through the opening parts and the window plates is received by a light-receiving device, the intensity of the light that is received during the polishing operation is 1% or more of the intensity of the projected light.
As a result, since there is no drop in the intensity of the light that returns to the light-receiving device, the polished thickness or polishing endpoint can be determined stably and with a high degree of precision utilizing the light signal that is detected by the light-receiving device. Furthermore, in order to perform an even more stable measurement, it is desirable that the intensity of the light that is received during the polishing operation be 5% or more of the intensity of the projected light.
An eighteenth embodiment of the present invention which is used in order to achieve the first aspect is the polishing apparatus of the sixteenth or seventeenth embodiments, which is further characterized by the fact that the window plates comprise a resin that has polishing characteristics comparable to the polishing characteristics of the polishing body.
As a result, even in cases where contact occurs between the window plates and the object of polishing (silicon wafer, etc.), the scratching of the polished surface of the object of polishing by the window plates, and non-uniform polishing, can be prevented.
A nineteenth embodiment of the present invention which is used in order to achieve the first aspect is a method used to adjust the gap between the outermost surface of the polishing body (i.e., the surface that contacts the object of polishing) and the surfaces of the window plates on the side of the outermost surface in a polishing apparatus which is the polishing apparatus of any of the sixteenth through eighteenth embodiments, and which has a function in which measurement light is directed onto the object of polishing from a light-projecting device via the window plates and the opening parts, this light is reflected by the object of polishing, and the returning light that again passes through the opening parts and the window plates is received by a light-receiving device; the polishing apparatus adjustment method being characterized by the fact that the method includes a stage in which the gap between the outermost surface of the polishing body and the surfaces of the window plates on the side of the outermost surface is adjusted on the basis of a signal measured by the light-receiving device.
In cases where the gap between the surfaces of the window plates on the side of the outermost surface of the polishing body and the outermost surface of the polishing body is too wide, the loss of light caused by the polishing agent that enters the recessed parts formed by the polishing body and the surfaces of the window plates on the side of the outermost surface of the polishing body becomes excessive, so that only an extremely weak signal can be obtained in the endpoint detection device. Accordingly, favorable measurement of the polished film thickness or polishing endpoint becomes impossible. On the other hand, in cases where the gap is too narrow, a signal caused by interference between the surfaces of the window plates on the side of the outermost surface and the layer of the polishing agent is added to the signal of the endpoint detection device; as a result, favorable measurement of the polished film thickness or polishing endpoint similarly becomes impossible.
In the present invention, the gap between the outermost surface of the polishing body (i.e., the surface that contacts the object of polishing) and the surfaces of the window plates on the side of the outermost surface is adjusted so that a signal that makes it possible to accomplish a favorable measurement of the polished film thickness or polishing endpoint while observing the signal of the light-receiving device can be measured by the endpoint detection device; accordingly, there are no problems of the type described above.
A twentieth embodiment of the present invention which is used in order to achieve the first aspect is a method for measuring the thickness of a polished film or the endpoint of polishing in which polishing is performed using the polishing apparatus of any one of the sixteenth through eighteenth embodiments, and the thickness of the polished film or endpoint of polishing is measured using a light signal received by a light-receiving device; this method being characterized by the fact that the signal measured by the measurement means that is used to measure the polished film thickness or polishing endpoint is not used in the measurement of the polished film thickness or polishing endpoint in cases where the signal measured by the measurement means is equal to a signal that is measured beforehand and stored in memory.
There may be instances in which the thickness of the polishing agent between the windows and the object of polishing is not constant during polishing, so that an inappropriate signal is obtained in the measurement of the polished film thickness or polishing endpoint. Examples of such inappropriate signals include extremely weak signals that are obtained in cases where the loss caused by the polishing agent is excessive, and signals to which is added a signal caused by interference of the layer of polishing agent present in the opening part on the window plate.
In the present invention, such inappropriate signals obtained during adjustment, etc., are stored in a memory device as pre-measured signals. During polishing, the signal measured by the measurement means is compared with the signals stored in the memory device, and in cases where measured signal is equal to any of the stored signals, the signal measured by the measurement means is not used in the measurement of the polished film thickness or the detection of the polishing endpoint. Accordingly, even in cases where the thickness of the polishing agent between the windows and the object of polishing is inconstant, so that the measurement might become unstable, erroneous measurement is eliminated in the measurement of the polished film thickness or polishing endpoint.
A twenty-first embodiment of the present invention which is used in order to achieve the first aspect is a polishing apparatus which is equipped with a polishing head that holds the object of polishing and a polishing body which is installed on a platen, and which polishes the object of polishing by causing relative motion between the polishing body and the object of polishing in a state in which a polishing agent is interposed between the polishing body and the object of polishing; this polishing apparatus being characterized by the fact that the apparatus has one or more opening parts formed in the platen, one or more opening parts formed in the polishing body, windows which are disposed so that they block at least portions of the opening parts formed in the polishing body, a device which measures the polished state by optically observing the polished surface of the object of polishing via the windows, and a moving device which moves the positions of the windows on the surface of the object of polishing, and the opening parts formed in the polishing body and the opening parts formed in the platen are superimposed, so that the windows are disposed on the platen via the moving device.
In the present invention, the gap between the surfaces of the windows on the side of the object of polishing and the polished surface of the object of polishing is controlled when the polished state of the object of polishing is observed by the device that measures the polished state by optically observing the polished surface of the object of polishing via the windows, so that the surfaces of the windows on the side of the object of polishing are not scratched by dressing or polishing, and so that a stable detection signal can be obtained. Accordingly, in-situ measurement of the polished state can be performed, and the frequency of replacement of the polishing body or windows can be reduced. As a result, the cost of polishing can be reduced.
A twenty-second embodiment of the present invention which is used in order to achieve the first aspect of the present invention is the twenty-first embodiment, which is characterized by the fact that the apparatus is further equipped with a device that senses the gap between the surfaces of the windows on the side of the object of polishing and the polished surface of the object of polishing, a device that senses the conditions of wear of the polishing body, or a device that senses both the gap and the conditions of wear.
As a result, the gap between the surfaces of the windows on the side of the object of polishing and the polished surface of the object of polishing can be sensed, so that the windows can be set in appropriate positions by means of the moving device. Accordingly, there is no scratching of the windows or object of polishing, and a stable detection signal can be obtained, so that in-situ measurement of the polished state is possible, and the frequency of replacement of the polishing body or windows can be reduced. As a result, the cost of polishing can be reduced.
A twenty-third embodiment of the present invention which is used in order to achieve the first aspect of the present invention is the twenty-second embodiment, which is characterized by the fact that the apparatus is further equipped with a control device that controls the gap between the surfaces of the windows on the side of the object of polishing and the polished surface of the object of polishing.
In the present invention, the gap between the surfaces of the windows on the side of the object of polishing and the polished surface of the object of polishing can be controlled by means of a control device. Accordingly, there is no scratching of the windows or object of polishing, and a stable detection signal can be obtained, so that in-situ measurement of the polished state is possible, and the frequency of replacement of the polishing body or windows can be reduced. As a result, the cost of polishing can be reduced.
A twenty-fourth embodiment of the present invention which is used in order to achieve the first aspect of the invention is the twenty-third embodiment, which is further characterized by the fact that the apparatus has a function which predicts the amount of wear of the polishing body from the polishing conditions, polishing time, dressing conditions and dressing time, and controls the gap between the surfaces of the above-mentioned windows on the side of the object of polishing and the polished surface of the object of polishing.
In the present invention, there is no scratching of the windows or object of polishing as a result of polishing or dressing, and a stable detection signal can be obtained, so that in-situ measurement of the polished state is possible, and the frequency of replacement of the polishing body or windows can be reduced. As a result, the cost of polishing can be reduced.
A twenty-fifth embodiment of the present invention which is used in order to achieve the first aspect of the present invention is the twenty-third embodiment, which is further characterized by the fact that the apparatus has a function which controls the moving device so that the gap between the surfaces of the above-mentioned windows on the side of the object of polishing and the polished surface of the object of polishing is maintained at a constant value.
In the present invention, there is no scratching of the windows or object of polishing as a result of polishing or dressing, and a stable detection signal can be obtained, so that in-situ measurement of the polished state is possible, and the frequency of replacement of the polishing body or windows can be reduced. As a result, the cost of polishing can be reduced.
A twenty-sixth embodiment of the present invention which is used to achieve the first and second aspects of the present invention is the twenty-third embodiment, which is further characterized by the fact that the apparatus has a function which controls the gap between the surfaces of the windows on the side of the object of polishing and the polished surface of the object of polishing in synchronization with the rotation of the platen.
In the present invention, there is no scratching of the windows or object of polishing as a result of polishing or dressing, and a stable detection signal can be obtained, so that in-situ measurement of the polished state is possible, and the frequency of replacement of the polishing body or windows can be reduced. As a result, the cost of polishing can be reduced.
The means which is used in order to achieve the second aspect is a semiconductor device manufacturing method in which the use of at least one of the apparatuses or methods of the present inventions in the sixteenth through twenty-sixth embodiments is included in the manufacture process.
In the present invention, the polished state and polishing endpoint can be stably detected in the wafer polishing process; accordingly, accurate wafers can be manufactured. Furthermore, since there tends to be no scratching of the windows through which the light used to detect the polished state and polishing endpoint passes, the frequency of replacement of the polishing body is reduced, so that the throughput can be increased, and costs can be reduced. At the same time, there tends to be no scratching of the wafer, either; accordingly, the wafer yield can be increased.